using System;

using System.IO;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(Path.GetFileName("abc.txt"));

        Console.WriteLine(Path.GetFileName("folder\\abc.txt"));

        Console.WriteLine(Path.GetFileName("C:\\some\\folder\\abc.txt"));

        Console.WriteLine(Path.GetFileName("folder/abc.txt"));

        Console.WriteLine(Path.GetFileName("C:/some/folder/abc.txt"));

    }

}